The present invention relates generally to apparatus and methods for mixing and dispensing fluids, and is particularly concerned with an apparatus and method for mixing fluids of differing viscosity such as various liquids, gases, or mixtures of liquids and gases.
Fluid mixing is required for many applications, such as in the chemical and petrochemical industries, foam producing for fire fighting, cleaning, bathing or the like, and aerated beverage production.
Fluid mixing systems may use pumps to achieve sufficient pressure for the particular application. For example, dog or other animal bathing systems must produce a foaming or soapy water output at sufficient pressure to penetrate matted hair and bring the detergent and water mixture to the skin surface. Sufficient agitation and lather is needed in order to cleanse the animal thoroughly. Other systems have utilized water line pressure and required driven devices for mixing the shampoo, water, de-fleaing agent or other chemicals. Such systems often have insufficient water pressure for agitation to produce complete cleansing.
Other fluid mixing devices have been proposed in the past which use venturi passages to draw fluids into a main fluid stream by suction or vacuum creation. For example, U.S. Pat. Nos. 3,822,217 and 3,853,784 of Rogers describe a foam-forming device in which a detergent inlet is provided at a smaller diameter portion of a venturi passage through which water is flowing. Detergent is injected in a thin jet into the passage, and mixes with the water. The mixture flows at higher velocity through the expanding portion of the venturi passage to produce a thorough mixing. Air is injected at a spaced location downstream of the detergent inlet.
In U.S. Pat. No. 2,800,313 of Targosh et al., a liquid mixing nozzle is described in which two diametrically opposite venturi passages are provided. A first inlet from a source of detergent is provided into one venturi passage, and an air inlet is provided into the other passage downstream of the detergent inlet. An air inlet opening is also provided into the first inlet, and this may be closed or partially closed by hand in order to vary suction drawing detergent into the passage.
It has been found that, when two fluid inlets for different viscosity fluids, which may be liquids and/or gases, are provided into the same venturi passage, back pressure from the lower viscosity fluid inlet can affect the amount of higher viscosity fluid drawn into the passage, even if the lower viscosity fluid inlet is downstream of the other inlet.